Gasification or liquefaction of coal using a metal reactant alloy composition

ABSTRACT

This invention relates to a method and apparatus for gasifying or liquifying coal. In particular, the method comprises reacting a coal with a molten aluminum or aluminum alloy bath. The apparatus includes a reaction vessel for carrying out the reaction, as well as other equipment necessary for capturing and removing the reaction products. Further, the process can be used to cogenerate electricity using the excess heat generated by the process.

FIELD OF THE INVENTION

The present invention relates to a method to gasify or liquefy coal andto capture and recover carbon, sulfur, hydrocarbons, and heavy metalsfrom the coal using a molten aluminum or alloy bath composed of aluminumor an aluminum alloy that includes, but is not limited to zinc, iron,copper, silicon and calcium alloys.

BACKGROUND OF THE INVENTION

Although a number of methods exist to gasify or liquefy coal, thesemethods are costly and in some cases create a secondary waste that canbe more of a problem than the actual gas stream itself. Currently, coalgasification or liquefacation methods create greenhouse gases such ascarbon monoxide carbon dioxide, as well as, other bi-products such astar, ammonia, and tar-water emulsions. Further, these processes alsoproduce slag, which currently must be land filled and there is currentlyno efficient method to recovery heavy metals, such as mercury, thattypically are found in coal. While these processes work, they requiresignificant energy input or create waste streams that must be disposedof at a cost to the operator and with potential future environmentalimpact. Thus, there is a need in the art for an improved method toeconomically gasify or liquefy coal while recovering the remainingcarbon, sulfur and any heavy metals.

SUMMARY OF THE INVENTION

The present invention provides an apparatus for gasifying or liquefyingcoal. The coal can be any coal from peat (a coal precursor) to lignite(60% carbon) to anthracite (90+ % carbon). The process utilizes a moltenaluminum or molten aluminum alloy bath. The aluminum can be alloyed withmetals that include, but are not limited to zinc, iron, copper, silicon,and calcium. The coal is ground and can be dried, and then the powder isintroduced into the bath below the surface. The powdered coal is forcedbelow the surface using an inert gas such as Nitrogen or argon. In theprocess excess heat is generated and can be used to facilitate otherprocesses such as cogeneration of power. As the coal is passed throughthe bath, the aluminum or aluminum alloy bath reacts with the coal tobreak it down to its elemental parts. These elements are then removedfrom the bath using a gravimetric process and a gas capture process. Theelements removed from the bath can include, but are not limited to,carbon, sulfur, hydrogen, nitrogen, mercury, copper, iron, as well asother heavy metals. The process can also produce methane and otherhydrocarbons. The elemental materials can be recovered and sold and thehydrocarbons are recovered and sold or burned to facilitate the process.The inert gas is reprocessed and reused.

The aluminum or aluminum alloy bath is able to remove oxygen compoundsby chemically reacting with them at high temperature. This allows thecarbon bonds of the coal to be broken, producing volatile organiccompounds, as well as elemental compounds.

This process has been evaluated in laboratory tests using ground lignitecoal. The ground coal was passed through molten aluminum. The flue gasproduced and the final alloy mass were analyzed using scanning electronmicroscope. (See Table 1).

TABLE 1 Process Mass Analysis MOL % H2 25.181 CO2 27.345 CO 14.265 C19.898 C2 2.824 C2 2.999 C3 0.939 C3 2.228 C4 0.199 C4 1.034 C4 0.000 C50.199 C6 and above 2.888 100

FIG. 1 shows the basic process flow. In the basic process, powdered coalis introduced below the surface of the molten metal bath 103 using aninjection feed system 101 through feed line 102. The elemental material,such as carbon, sulfur and the like, is captured 104, less densesecondary compounds are removed from the surface of bath 105, and densersecondary compounds are removed from the bottom of the bath 106. Whilethis has been described as a method to gasify or liquefy coal, use ofthis method to other organic compounds, such as, for example, peat,wood, and grass are also contemplated.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, reference isnow made to the following descriptions taken in conjunction with theaccompanying Figures and drawings, in which:

FIG. 1 shows the basic process flow;

FIG. 2 shows a typical process flow; and

FIG. 3. shows a detailed cross sectional view of the reaction vesselwall.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a process to gasify or liquefy coal. Theprocess utilizes a molten aluminum or molten aluminum alloy bath. Theprocess utilizes a molten aluminum bath as the reactant. The coal, whichis introduced below the surface of the molten aluminum bath, reacts withthe aluminum to decompose the coal. In the process, elemental carbon,sulfur, copper, iron, and heavy metals and molecular hydrogen, nitrogen,methane, and other hydrocarbons are removed from the molten bath. Theproducts can be sold and the nitrogen is either vented to the atmosphereor captured.

The process utilizes a molten metal as the primary reactant. In thepreferred embodiments the molten metal is aluminum or an aluminum bath.The aluminum can also be alloyed with other elements including, but notlimited to, zinc, iron, copper, silicon, magnesium, and calcium. Othermetals and metal alloys such as calcium and silicon are also envisioned.The flue gas stream, which contains oxygen containing greenhouse gasesproduced by combustion processes, is passed through the aluminum alloybath to remove the oxygen-containing gases from the flue gas stream.

In the process, excess heat is generated and can be used to facilitateother processes such as cogeneration of power. The excess generated bythe process is a function of the makeup of the greenhouse gases in theflue gas feed.

When the coal contains other compounds, those compounds can also bedecomposed or captured. For example, if the coal contains inorganiccompounds, such as chlorine, the process will produce an aluminum salt,in this case aluminum chloride. The present invention also provides amethod and apparatus for capturing heavy metals, such as, but notlimited to mercury, which is often found in coal. In the process, themolten metal bath breaks down the metal compounds as they are introducedinto the molten metal bath. As additional aluminum is added to the bath,the heavy metals settle to the bottom of the reaction vessels and areremoved from the reaction vessel. While some aluminum may be entrainedin the heavy metals that are removed from the bottom of the reactionvessel, the aluminum can be removed and refined and the heavy metals canbe captured.

A detailed process flow is shown in FIG. 2. While the process describeddiscusses processing coal, other organic materials can be processedusing the invention. The ground coal is introduced into the treatmentprocess through blower feed line 211. Blower 210 is used to inject theground coal into reaction vessel 220 through injection line 212.Injection line 212 introduces the ground coal stream, which is entrainedin an inert gas such as nitrogen, below the surface 222 of the moltenaluminum compound 226. Injection line 212 must be sufficiently below thesurface 222 of the molten aluminum compound 226 to allow for sufficientmixing. The heavy products of the reaction, typically the heavy metalsdescribed above will settle out in the reaction vessel. The reactionvessel typically has a sloped bottom, however other designs such conicaland the like can be utilized. Once the heavy products settle out, theyare collected using collection lines 223, 224, and 225. Collection lines223, 224, and 225 allow for heavy metals of different densities to beremoved. Depending on the size of the process, the heavy products can becontinuously removed or a batch removal process can be used.

Reaction vessel 220 also includes an aluminum feed line 221, which isused to supply additional aluminum compound to replace that consumed bythe reaction with the ground coal. Additional heat may be requiredduring start-up, for example. Heater 227 is provided for this purpose.Heater 227 can be any type heater, including radiative, inductive, andconvective. For example, heater 227 would be a microwave heater or aradio frequency heater wherein the frequency is tuned for the metalalloy used.

Thus, the heat generated by the process must be removed. Section A,which is shown in more detail in FIG. 3 shows one way the heat can beremoved from the process. The reaction vessel 220 is lined with arefractory material 310, which protects the vessel wall 320. Coolingplate 330 is attached to the vessel wall 320 and cooling water iscirculated in the channels created between the cooling plant 330 and thevessel wall 320. Insulation 340 surrounds the cooling plate to maximizeheat recovery, as well as for safety purposes. Once the cooling waterpicks up the heat generated from the process, it can be either sent to acooling tower or the heat can be recovered and used for other purposes.If the process is used in a facility that needs a hot water source, thenthe heat recovery system can be designed for this purpose. However, theheat can also be used to generate electricity.

Turning back to FIG. 2, a steam turbine electric generation process isrepresented. In this case, the cooling water is introduced thoroughcooling feed 228. As the cooling water travels around the reactionvessel 220, it picks up heat and steam is generated. The steam generatedis then sent via steam line 229 to steam turbine 232. The steam passesthrough the turbine and as it condenses, turns the turbine blades ofturbine 232. Turbine 232 is coupled to generator 231. As the turbineturns the rotor of generator 231 though the stator, it generateselectricity. While this process is only briefly described, this steamturbine-electric generator process is well known in the art. And anysteam turbine-electric generator process could be utilized.

Also, as described above, the reaction will also produce elementalcarbon, elemental sulfur, molecular nitrogen and molecular hydrogen.These will be removed from the reaction vessel using blower 250. Blower250 will pull high temperature elemental carbon, elemental sulfur,molecular nitrogen and molecular hydrogen from the reaction vessel 220through heat exchanger feed line 241 into heat exchanger 240. Heatexchanger 240 will then cool this material to enable further processing.Any hydrocarbons that are produced may also be condensed in heatexchanger 240. These liquid hydrocarbons can be collected for furtheruse or sale. Heat exchanger 240 can be any heat exchanger, however inthe preferred embodiment, heat exchanger 240 is a forced air heatexchanger, however other heat exchangers, are also envisioned. Theprocess steam then leaves the heat exchanger through line 242 and passesthrough blower 250 and blower discharge line 252 into two cycloneseparators. The first separator 260 separates out carbon from processstream. The carbon is collected though separation line 263. Theremaining process stream through line 262 proceeds to the secondseparator 270, which separates out sulfur from the process stream. Thesulfur is collected through separation line 273. The remaining processstream, which may include gaseous nitrogen and hydrogen, is then sentthrough line 272 and separated in cryo unit 280. In this unit, the gasstream is cooled further and to allow the components to be separatedinto different components that are sent through lines 282 and 283.

Although the present invention and its advantages have been described indetail, it should be understood that various changes, substitutions andalterations can be made herein without departing from the spirit andscope of the invention as defined by the appended claims. Moreover, thescope of the present application is not intended to be limited to theparticular embodiments of the process, machine, manufacture, compositionof matter, means, methods and steps described in the specification. Asone of ordinary skill in the art will readily appreciate from thedisclosure of the present invention, processes, machines, manufacture,compositions of matter, means, methods, or steps, presently existing orlater to be developed that perform substantially the same function orachieve substantially the same result as the corresponding embodimentsdescribed herein may be utilized according to the present invention.Accordingly, the appended claims are intended to include within theirscope such processes, machines, manufacture, compositions of matter,means, methods, or steps.

What is claimed is:
 1. A method for producing liquefied products fromsolid coal particles, the method comprising: injecting a stream of coalinto a molten metal in a reaction vessel at a sufficient distance belowthe upper surface of the molten metal for mixing the coal into themolten metal; reacting the stream of coal with the molten metal toproduce a liquefied product; separating, by settling, the liquefiedproduct from the molten metal within the reaction vessel; removing theliquefied product from the reaction vessel through a lower outlet in thereaction vessel; removing reaction gas from the reaction vessel; andremoving particulate matter from the reaction gas using a separator. 2.The method of claim 1, wherein the reaction vessel comprises a reactionvessel wall, a refractory material, and a cooling plate, wherein thecooling plate forms a channel for a cooling fluid between the coolingplate and the reaction vessel wall.
 3. The method of claim 1, whereinthe molten metal comprises aluminum.
 4. The method of claim 1, whereinthe molten metal comprises aluminum alloy.
 5. The method of claim 1,wherein the molten metal comprises at least one alloy material selectedfrom the group consisting of silicon, magnesium, zinc, copper, iron, andcalcium.
 6. The method of claim 1, wherein the molten metal is silicon.7. The method of claim 1, wherein the molten metal is silicon alloy. 8.The method of claim 1, further comprising replacing molten metalconsumed by reaction in the reaction vessel.
 9. The method of claim 1,further comprising using a heat exchanger to produce gasified and/orliquefied products from the reaction gas.
 10. The method of claim 9,further comprising separating particulate matter from the gasifiedand/or liquefied products.
 11. The method of claim 1, wherein theliquefied product is comprised of two or more components of differentdensities.
 12. The method of claim 11, wherein removing liquefiedproducts from the reaction vessel through a lower outlet in the reactionvessel comprises: removing a first component of a lighter density from afirst collection line; and removing a second component of a heavierdensity from a second collection line.